This patent application is a continuation-in-part to patent application Ser. No. 06/925,084 entitled "Vortex Shedding Flowmeter with Swivel Stress Transmitter" filed on Oct. 30, 1986; Ser. No. 07/012,680 entitled "Vortex Shedding Flowmeter with Mechanically Amplifying Pressure Sensor" filed on Feb. 9, 1987; Ser. No. 07/031,902 entitled "Three-in-one Vortex Shedding Flowmeter" filed on Mar. 30, 1987; and Ser. No. 07/105,265 entitled "Vortex Shedding Flowmeter" filed on Oct. 7, 1987.
The phenomena of the vortex shedding from a bluff body immersed in the fluid stream occur at Reynolds numbers greater than a few hundred in a clear and regular manner, where the Reynolds number is defined as the product of the bluff body width and the fluid velocity divided by the kinematic viscosity of the fluid. For the Reynolds number greater than 1,000 and less than 400,000, the vortex shedding frequency is linearly proportional to the fluid velocity and the amplitude of the alternating lift forces on a wing placed downstream to the bluff body is proportional to the dynamic pressure of the moving fluid medium, which dynamic pressure is defined as one half of the fluid density times the square of the fluid velocity. The vortex shedding phenomena provides the physical principles for designing a flowmeter that determines: (1) the fluid velocity by measuring the vortex shedding frequency; and (2) the dynamic pressure by measuring the amplitude of the alternating lift forces on the wing sensor in the Reynolds number range greater than 1,000 and less than 400,000, which range is equivalent to the air flows under the standard condition faster than a few feet per second and the water flows faster than a fraction of a foot per second. The existing art of the flowmeter employing the vortex shedding principles only measures the fluid velocity based on the vortex shedding frequency for air flows faster than 25-30 feet per second and water flows faster than 1-2 feet per second, which indicates that the level of the existing art in the vortex shedding flowmeter technology is at an infantile stage.